1. Field of the Application
This application relates generally to expansion couplings for coupling electrical conduits. More particularly, the application relates to an expansion coupling internally maintaining an electrical ground across the electrical conduits.
2. Description of the Related Art
Electrical conduit is often used to enclose electrical wiring. These conduits may be metallic, and in certain instances are required to be grounded. Conduits enclosing such electrical wiring may be interconnected with electrical couplings. Some of these couplings allow for thermal expansion of the electrical conduits, permitting relative longitudinal movement between the conduits in response to temperature changes. These couplings must not only allow for thermal expansion of the conduits, but also must maintain ground continuity across the conduits during such expansion and longitudinal movement.
When applicable, it is well known to use expansion couplings to connect conduits. Some expansion couplings use an external bonding jumper to provide ground continuity. However, external bonding jumpers may become loose and are susceptible to tampering and theft. Accordingly, some expansion couplings have been designed with internal grounding mechanisms. Examples of expansion couplings with internal grounding can be found in U.S. Pat. Nos. 3,783,178 and 4,250,350. One problem associated with expansion couplings with internal grounding mechanisms is that electrical inspectors cannot always tell if the expansion coupling is properly grounded, and oftentimes redundant external bonding jumpers are installed to allow the expansion coupling to pass inspection. Thus, there is a need to design an expansion coupling that can be readily disassembled in the field to allow electrical inspectors to verify proper grounding is in place.
In addition, expansion couplings that allow for thermal expansion typically must allow for relative longitudinal movement of a conduit end to move within the expansion coupling housing. As a result, a seal may be used to prevent moisture and contaminants from entering the expansion coupling. Thus, there is a need to provide a seal to allow relative longitudinal movement of a conduit end within the expansion coupling that is effective at preventing moisture and contaminants from entering the expansion coupling.
These as well as other aspects and advantages will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, it should be understood that the embodiments described in this summary and elsewhere are intended to illustrate the invention by way of example only.